oldColorDiff - Allowed difference in old color to be able to widen replaced color tone.

newColorArgb - New color ARGB value to replace old color with.

replaceNonTransparentColors

public void replaceNonTransparentColors(int newColorArgb)

Replaces all non-transparent colors with new color and preserves original alpha value to save smooth edges.
Note: if you use it on images without transparency, all colors will be replaced with a single one.